The invention belongs to the field of engine arrangements of the type comprising an internal combustion engine having an intake line, an exhaust line and an EGR line for recirculating gases from the exhaust line to the intake line, wherein at least one turbine is located on the exhaust line, wherein the arrangement comprises a water vapor generating arrangement using exhaust gases energy to transform liquid water into water vapor, and wherein said water vapor is injected in the exhaust line upstream of the turbine.
Such arrangements take advantage of the heat which is carried in the exhaust gases, and which is generally simply released in the atmosphere and lost, by transforming the heat into mechanical energy which is recovered on the turbine shaft thanks to the expansion and/or cooling of the heated water vapor in the turbine. The recovered energy can be used in a variety of ways.
Document JP-2001.132.538 discloses an engine arrangement of the type above wherein the water circuit comprises two heat exchangers for heating the water and transforming it into vapor. The first exchanger takes heat from a charge air circuit, i.e from air which has been compressed by a turbo-compressor before being introduced in the internal combustion engine. Such air is not very hot, typically in the range of 130 to 200° C. The second heat exchanger takes heat from the exhaust gases which circulate in the exhaust line downstream of the turbine. These gases, although quite hot, have undergone an expansion in the turbine whereby their heat has been diminished by up to 100° C., down to 300° C. as a mean temperature. Therefore, although the system shown in this document may be well suited for certain uses, such as a stationary power generation units, it may not be suited for other applications such as for the propulsion of a vehicle. Indeed, while stationary power engine arrangements operate at steady conditions where the temperatures of the exhaust gases are well controlled within a limited range of temperatures, vehicle applications require that the engine arrangement works at varying loads, which can lead to very different exhaust temperatures. There is therefore a need to design an improved arrangement where operation of the water vapor generating arrangement can be guaranteed over a wider range of operating conditions.
In view of the above, the invention provides for an engine arrangement of the type above, characterized in that the EGR line is branched off the exhaust line upstream from the turbine and in that water vapor generating arrangement comprises at least one EGR/water heat exchanger for exchanging heat between the EGR line and the water to be vaporized.